Protection of metallic films from galvanic reactions on photographic layers or the like being applied to them



Patented Feb. 23, 1932 UNITED STATES PATENT OFFICE CHRISTIAN SEMENITZAND SIIEGrIERIED- LOEWENTHAL, OF BERLIN, GERMANYQAS- SIGNORS TO REINOLDKU'PFEIR, OF BERLIN, GERMANY PROTECTION OF METALLIC FILMS FROM GALVANICREACTIONS ON PHOTOGRAPHIC LAYERS OR THE LIKE BEING APPLIED TO THEM NoDrawing. Application filed August 9, 1930, Serial No. 474,220, and inGermany May 10, 1929.

lVhen photographic or similar layers are applied to metallic films, forexample to thin aluminum foils or films, it is found that when theso-coated films are introduced into photographic baths, that is, thebaths for treating the photographic layers, the metal salts dissolved inthe bath and depositcd on the layers bring about galvanic reactionsbetween such salts and the carrier metal which leads to thedeterioration of the photographic layer and to corrosion of the carriermetal.

Similar deleterious galvanic reaction may take place not only in thephotographic bath; but also in applying 0r drying the photographiclayer.

The present invention relates to means to prevent or greatly reduce suchgalvanic action. As the salts, above referred to, are either morenegative or more positive than the carrier metal, the salt and the metalform a galvanic couple with a resultant electro- 'motive force. Byapplying during the rier metal in such bath in such direction as Y tobuck and nullify the effect of the galvanic current due to thedifference of potential set up between the metallic film and the metalin the salt bath.

2. A step in the fprocess for treating metallic photographic lms inliquid baths .containing solutions of metallic salts, comprising passinga Weak direct current through the carrier metal'in such bath in suchdirection as to buck and nullify the eflect of the galvanic current dueto the difference of potential set up between the metallic film and themetal in the salt bath.

